Vibration by Bubba???
Thread Starter
Racer
Joined: Mar 2009
Posts: 331
Likes: 1
From: Brooklin Ontario
Vibration by Bubba???
I have a 427 L68 with a THM 400 transmission. Been investigating vibrations. everything on the car is correct L68 it seems but the flexplate is for a 454 (original weight installed). The harmonic balancer is 7" diameter so I believe it is 427 correct.
any quick way I can I.D. the crank to be sure I'm on the right track?
Should I just buy a 427 balancer and flexplate and see what happens. Thats what I'm leaning towards.
All opinions welcome and appreciated!
Later, Roger.
any quick way I can I.D. the crank to be sure I'm on the right track?
Should I just buy a 427 balancer and flexplate and see what happens. Thats what I'm leaning towards.
All opinions welcome and appreciated!
Later, Roger.
Le Mans Master
Joined: Jun 2008
Posts: 5,284
Likes: 235
From: Rockledge FL
that is your problem.
a 454 harmonic balancer has a weight to counter the weight on the flexplate. the balancer and flexplate for a 427 have no weights. buy a flexplate for a 427 with a th400 and it should straighten out. check your balancer while you are it. you can see the weight if it is a 454 balancer.
a 454 harmonic balancer has a weight to counter the weight on the flexplate. the balancer and flexplate for a 427 have no weights. buy a flexplate for a 427 with a th400 and it should straighten out. check your balancer while you are it. you can see the weight if it is a 454 balancer.
Le Mans Master
Joined: Mar 2008
Posts: 5,948
Likes: 72
From: Oxford MA-----You just lost the game!!!!
chevy 427 is internally balanced, 454 is externally balanced, so if you have a 454 flexplate on a 427, I guess it might cause problems, I don't really know a whole lot about engine balancing. But I do know that on an internally balanced engine the harmonic balancer isn't really a balancer, per se, It's just a dampener.
Scott
Scott
Thread Starter
Racer
Joined: Mar 2009
Posts: 331
Likes: 1
From: Brooklin Ontario
Drifting
Joined: Jun 2010
Posts: 1,781
Likes: 15
From: Oxford Ohio
Was the engine balanced when it was built? I'm suspecting not as the shop that did the balancing would have determined during the proceedure, that the plate or balancer were incorrect.
The changing of those parts won't balance your engine as those parts are balanced to your bottom end. So just the changing of those parts MAY not end your vibrations.Did you get a balance sheet with your engine rebuild?
The changing of those parts won't balance your engine as those parts are balanced to your bottom end. So just the changing of those parts MAY not end your vibrations.Did you get a balance sheet with your engine rebuild?
Thread Starter
Racer
Joined: Mar 2009
Posts: 331
Likes: 1
From: Brooklin Ontario
Was the engine balanced when it was built? I'm suspecting not as the shop that did the balancing would have determined during the proceedure, that the plate or balancer were incorrect.
The changing of those parts won't balance your engine as those parts are balanced to your bottom end. So just the changing of those parts MAY not end your vibrations.Did you get a balance sheet with your engine rebuild?
The changing of those parts won't balance your engine as those parts are balanced to your bottom end. So just the changing of those parts MAY not end your vibrations.Did you get a balance sheet with your engine rebuild?
All I can assume for now, based on everything else on the car is L68 427 correct as it should be according to GM and the serial # (canadian car), it has an incorrect flexplate. I am going to change the flexplate and harmonic balancer (which is correct) and if I still have vibes after that, its time to pull the engine, which I really didn't want to do this winter.
What do you all think??
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Thread Starter
Racer
Joined: Mar 2009
Posts: 331
Likes: 1
From: Brooklin Ontario
Thread Starter
Racer
Joined: Mar 2009
Posts: 331
Likes: 1
From: Brooklin Ontario
Ok Pulled the balance. the unit looks really old and beat to hell. Lots of chips taken out of the engine side outer perimeter. Don't want to know how that happens. it is correct for the 69 427. four of the holes on one side are filled. are these weights?
